Soft tissue and dentoskeletal changes associated with mandibular molar distalization using clear aligner therapy: a retrospective cross-sectional CBCT study

This retrospective study aims to determine the changes in soft and hard tissue parameters after mandibular molar distalization using clear aligners and its correlation with the treatment duration, and the amount of molar distalization. 23 adult patients (15 Female, 8 Male) were included in this study. Cone beam computed tomography (CBCT) images were evaluated for soft and hard tissue parameters especially lower facial profile including lip and chin. Paired sample t test and the Wilcoxon signed rank test were used to compare changes before and after molar distalization. Bivariate Pearson correlation analysis was conducted to assess relationships between treatment duration and amount of distalization and changes in lower facial profile. Multiple linear regression (MLR) was applied to predict the changes based on amount of distalization and incisors inclination. Significant increase in mandibular plane angle based on MP-FH angle (25.41 ± 5.08, 26.16 ± 5.47, P = 0.021). Furthermore, the total anterior facial height (N-Me) and lower anterior facial height (ANS-Me) significantly increased (135.63 ± 9.39, 136.79 ± 9.77, P = 0.021 and 71.33 ± 5.92, 72.33 ± 1.32, P = 0.030 respectively). However, the lower lip thickness decreased significantly (13.31 ± 3.80, 12.36 ± 3.24, P = 0.001), as well as lower lip length (19.78 ± 2.80, 18.66 ± 2.58, P = 0.003). Pearson correlation analysis revealed significant correlation between the treatment duration and the amount of distalization across most of the parameters. Mandibular molar distalization provides stable mandibular control with negligible rotational or sagittal changes, minimal facial height increase, and reductions in lower lip thickness and length without significant sagittal displacement.